js 點擊input和textarea 文字框消失

<input name="shouji" type="text"  value="輸入手機號簡易註冊"  onclick="clearDefaultText(this,'輸入手機號簡易註冊')"/>

 

 

function clearDefaultText (el,message)
{
var obj = el;
if(typeof(el) == "string")
obj = document.getElementById(id);
if(obj.value == message)
{
obj.value = "";
}
obj.onblur = function()
{
if(obj.value == "")
{
   obj.value = message;
}
}
} 

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<textarea name="morencontect" rows="8"   id="contect" onfocus="ClearDefault(this)" onblur="AddDefault(this)">我想旅遊</textarea>

var defaultvalue="我想旅遊";
function ClearDefault(element)
{
 
   if(element.value==defaultvalue)
   {
     element.value = "";
   }
}
function AddDefault(element)
{
 
  if(element.value=="")
  { element.value =defaultvalue; }
}